FYFD

Tag: pollution

  • Burning Oil Spills With Fire Whirls

    Burning Oil Spills With Fire Whirls

    Though they are relatively infrequent, large marine oil spills, like 2010’s Deepwater Horizon, are devastating and incredibly difficult to clean up. In many locations, the “best” option for responding to such disasters is burning off the oil before it can absorb enough water to sink. But these floating fires leave behind unburned oil and produce soot. To enhance the burn, researchers are looking at the possibility of triggering large-scale fire whirls.

    Often seen in wildfires, these fire vortices are intense and localized. Researchers made a more than 5-meter tall version in these experiments by arranging three walls that spun up the in-flowing air. The fire whirl sat above a pool of water topped in a layer of oil that served as the whirl’s fuel.

    Within the whirl, the fire’s burn rate was 40% higher than a typical pool fire, and soot production was 40% lower–showing that fire whirls can burn cleaner. But the whirls are more finicky to start and maintain. It’s not yet clear whether such intense whirls are possible in the chaotic conditions on the ocean. (Research and image credit: W. Cui et al.; via Eos)

    View of a large-scale fire whirl experiment built around an oil spill on a pool.
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    Dispersing Pollutants via Smokestack

    In our industrialized society, pollutants are, to an extent, unavoidable. Even with technologies to drastically reduce the amount of pollutants leaving a factory or plant, some will still get released. It’s up to engineers to make sure that those released spread out enough that their overall concentration does not pose a risk to public health. In this Practical Engineering video, Grady explains some of the physics and engineering considerations that go into this task.

    As he demonstrates, taller smokestacks speed up the buoyant exhaust plume (to an extent), which exposes the plume to higher winds, greater turbulence, and, thus, quicker dispersal. But atmospheric conditions and even nearby buildings all affect how a plume spreads. (Image and video credit: Practical Engineering)

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  • Measuring Microfibers in Turbulence

    Measuring Microfibers in Turbulence

    Microplastic pollution is on the rise, especially in waterways. Microfibers — millimeters in length but only microns in diameter — are especially prevalent, as they get washed out of synthetic clothing. Collecting these pollutants first requires understanding how they move and cluster in turbulent flows. Researchers investigated that using a small water channel and high-resolution cameras.

    The team followed microfiber strands as they moved through turbulence, paying special attention to how the fibers tumbled (rotating about their short axis) and spin (rotating around their long axis). How much fibers tumbled depended on the turbulence level; with more intense turbulence, the fibers tumbled more. Rates of spinning, they found, were consistently even higher than those for tumbling. By better understanding how microfibers behave in turbulence, we’ll be able to, for example, predict how far plastics will travel before settling to the ocean floor. (Image credit: Adobe Stock Photos; research credit: V. Giurgiu et al.; via APS Physics)

  • How Large Particles Get in Sea Spray

    How Large Particles Get in Sea Spray

    When bubbles burst at the ocean’s surface, they eject droplets that can carry high concentrations of contaminants like pollutants, viruses, and microplastics. Previous theories posited that only particles smaller than the microlayer surrounding the bubble could make their way into these drops, but new work shows otherwise.

    As bubbles rise to the surface, they carry particles on their surface, collecting them to a concentration that’s even higher than the surrounding seawater. But which particles make it into the air depend on the details of what happens when the bubble pops. Previously, researchers assumed that the thin microlayer of fluid surrounding the bubble was uniform, but that turns out not to be the case. As the bubble pops, some regions of the microlayer stretch and thin, while others grow thicker. The thicker the microlayer, the larger the particles it can pull along. In their single-bubble experiments, the researchers found that 15- and 30-micrometer plastic beads — representing oceanic microplastics — appeared in high concentrations in ejected droplets.

    This animated simulation shows how fluid along the edge of a bubble makes its way into ejected droplets. Green particles indicate fluid from the left half of the bubble; blue shows fluid from the right side.
    This animated simulation shows how fluid along the edge of a bubble makes its way into ejected droplets. Green particles indicate fluid from the left half of the bubble; blue shows fluid from the right side.

    Environmental scientists are keen to understand these mechanisms because they link our oceans and atmosphere, potentially affecting rainfall, pollution spread, and epidemiology. (Image, video, and research credit: L. Dubitsky et al.; via APS Physics)